<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style type="text/css">
        .right>div{
            height: 500px;
        }

        .right>div:nth-of-type(even){
            color: red;
        }

        .right>div:nth-of-type(odd){
            color: blue;
        }
            
    </style>
</head>
<body>
    <div class="left">
        <a href="#a">a</a>
        <a href="#b">b</a>
        <a href="#c">c</a>
        <a href="#d">d</a>
    </div>
    <div class="right">
        <div class="aa" id="a">
            aaaaa
        </div>
        <div class="bb" id="b">
            bbbbb
        </div>
        <div class="cc" id="c">
            ccccc
        </div>
        <div class="dd" id="d">
            ddddd
        </div>
    </div>
</body>
</html>